The present disclosure relates to sensing the level of a medical fluid in a container.
Knowing a volume or level of a medical fluid in a container is important in many medical fluid applications. For example, it may be important to know when a medical fluid supply is running low, so that a new source of fluid can be installed or opened. In a reusable container, it may be important to know the liquid level to ensure that the container is not overfilled but has enough supply for whatever use is necessary.
Certain existing medical device sensors require that an associated pump or moving part be stopped before a fluid level can be sensed accurately. Stopping the therapy to take a measurement results in a point in time system as opposed to a true real time system. Stopping therapy also lengthens overall therapy time.
Other existing sensors use a capacitive probe or capacitive element that measures a distance between the probe and the fluid. Capacitive sensors rely on the conductivity of the fluid and thus may not be desirable in medical applications in which the conductivity of a measured fluid changes during therapy. For example, in dialysis applications, the conductivity of dialysis fluid may fluctuate as the fluid is regularly modified, refreshed, and rejuvenated. Dialysis and other medical fluid applications may accordingly provide a container that holds different fluids having different conductivities at different times. In such applications, it may be advantageous to have a level sensor that is at least substantially independent of or unaffected by fluid conductivity.
Another class of existing sensors relies on radiating a signal from a transmitter to a receiver and measuring the attenuation of the radiated signal to determine whether fluid exists at various points inside a container. Radiation in medical applications is undesirable because it can interfere with nearby equipment and may be harmful to the patient.
Other existing sensors rely on invasive probes that must be in contact with the measured fluid or need to be located inside the container where the measured fluid resides. The probes present sterility and disinfection issues. Residue can build up on the probe, requiring additional maintenance and cleaning. Probe systems can also make swapping or changing fluid containers cumbersome. Opening a new container to insert a probe requires the container to be openable and presents further sterilizing issues. It would therefore also be advantageous to have a non-invasive sensor that does not require physical contact with the fluid and does not need to be placed inside the container.
A need accordingly exists for an improved medical tank level sensor.